JP4286683B2 - Semiconductor laser - Google Patents

Description

  The present invention relates to a semiconductor laser particularly suitable for use in a pickup light source such as a CD, a DVD (digital versatile disk), a DVD-ROM, or a data-writable CD-R / RW. More specifically, the present invention relates to a semiconductor laser that has a high COD level even for high output and can have a long lifetime.

  For example, as shown in FIG. 5, the semiconductor laser is formed by laminating a semiconductor layer so that a stripe-shaped light emitting region is formed on a semiconductor substrate 21 to form a semiconductor laminated portion 22, which is cleaved from a wafer in a bar shape. Resonator end faces are formed, and first and second dielectric films 23 and 24 are formed on both end faces thereof to adjust the reflectivity of both end faces, and are further formed into chips by dicing or the like from a bar shape. With this structure, light is mainly emitted from one end face (front end face) of the stripe-shaped light emitting region, and the other end face (rear end face) emits a slight output used for monitoring oscillation output. The reflectivity is adjusted. Then, as shown in FIG. 5, it is mounted on a submount 25 made of Si substrate or AlN, and incorporated into an optical pickup or the like.

Since the first and second dielectric films 23 and 24 provided on the end face mainly use the output that oscillates as emitted from the front end face as described above, the reflectivity of the rear end face is reduced by reducing the reflectivity of the front end face. The degree of reflectivity, and whether the dielectric film is formed as a single layer or multiple layers are determined by the target semiconductor laser, and are variously determined. It is formed in the configuration. For example, an Al ₂ O ₃ film having a film thickness of 0.15 wavelength at the optical distance and a Si film having a film thickness of 0.04 wavelength at the optical distance are provided on the front end face, respectively. The low reflectivity makes it easy to obtain a high output and prevents destruction (COD) due to heat at the end face. On the rear end face, for example, Al ₂ O ₃ having an optical distance of 0.25 wavelength is used. A configuration has been proposed in which four layers of SiO ₂ are provided alternately to form a high reflectance of 92% (see, for example, Patent Document 1).
Japanese Patent Publication No. 7-32287

  As described above, the semiconductor laser is provided with a dielectric film on the cleavage surface of the stripe-shaped light emitting region so that the front end face and the rear end face have a desired reflectance with respect to the oscillation wavelength. It has been adjusted. However, when the semiconductor laser starts operating, current concentrates in the light emitting region and emits light, so that the temperature of the light emitting region rises and the oscillation wavelength becomes longer due to the temperature rise. For this reason, there is a problem that the threshold current increases and the light emission efficiency decreases as the temperature of the light emitting region rises, and the reflectivity changes due to the shift of the oscillation wavelength and the output varies.

  Further, in the high-power semiconductor laser, the first dielectric film is formed so that the reflectance on the emission end face side is reduced and the output can be easily taken out from the front end face. On the other hand, the reflectance of the front end face is not as good as it is small due to the influence of noise due to return light, and there are cases where it is desired to adjust the reflectance to a desired reflectance as described above. Since this dielectric film is formed by sputtering or the like, if it has a desired reflectance, it is preferably as thin as possible in terms of manufacturing cost, and is generally formed as a thin film having a desired reflectance. By the way, in the case of high output such as a CD-R / RW semiconductor laser, the interface between the cleaved surface of the semiconductor laser chip and the first dielectric film becomes an antinode part of the electric field distribution, particularly 80 mW or more. In a high-power semiconductor laser, even if the first dielectric film is formed to have a low reflectivity of about 8.5%, the temperature of the first dielectric film rises and COD (catastrophic optical damage) ) There is a problem that the level is lowered and it is easy to break.

  The present invention has been made in view of such a situation. Even when the temperature of the semiconductor laser rises and the oscillation wavelength changes, the output can be stabilized, and the output side end face can be used for high output. An object of the present invention is to provide a semiconductor laser having a structure capable of improving the COD level of a semiconductor laser in which the COD level of the (front end face) is likely to be lowered.

  The present inventor has a problem that the oscillation output cannot be accurately controlled as the temperature rises due to the operation of the semiconductor laser, and a high output (for example, 200 mW) at a high temperature (for example, 75 ° C.) with a high output semiconductor laser or the like. In this accelerated life test, the problem of the generation of a semiconductor laser that breaks in a short time of 100 to 250 hours was investigated through extensive studies. As a result, with a normal dielectric film thickness that can achieve the desired reflectance, the reflectance changes when the wavelength of light is changed with the thickness being constant, and the reflectance increases as the wavelength increases. Therefore, when the oscillation wavelength becomes longer, the external differential efficiency decreases, the output further decreases, and the heat generated at the cleavage end surface of the laser chip is not sufficiently dissipated. It has been found that the semiconductor crystal at the surface melts and its end face breaks down.

  By adopting the thickness of the dielectric film in which the change in reflectance with respect to the change in wavelength near the desired wavelength is negative, the reflectivity decreases as the oscillation wavelength increases. The external differential quantum efficiency is improved and the output is increased, and the influence can be suppressed, and the dielectric film formed on the front end face is made of aluminum oxide having a high thermal conductivity and is made as thick as possible. It has been found that the COD level can be kept high even with a high-power semiconductor laser of 250 mW or more.

A semiconductor laser according to the present invention includes a semiconductor substrate, a semiconductor laminate laminated on the semiconductor substrate, forming a stripe-shaped light emitting region, and laminating a semiconductor layer so as to oscillate at an oscillation wavelength λ, and the semiconductor A first dielectric film formed at one end of the stripe-shaped light emitting region of the laminated portion so as to have a predetermined reflectance with a low reflectance, and a high reflectance at the other end of the stripe-shaped light emitting region and a second dielectric film is formed to be, the first dielectric film is formed by an aluminum oxide film, the reflectance changes to the thickness of the aluminum oxide film before Symbol oscillation wavelength λ is constant When the oscillation wavelength is increased, the curve of the reflectance changes when the oscillation wavelength is increased and the aluminum oxide film is almost parallel to the desired thickness. become, And, the thickness gradient of the curve of the reflectance change becomes positive, the Rukoto thickness is set in the aluminum oxide film, due to the temperature rise by lowering the reflectance due to the change in the oscillation wavelength due to temperature rise The output is reduced by an increase in threshold current, and the optical distance is set to a thickness of 0.6λ or more.

  Here, the optical distance is an optical path length, and means nL when light passes through a medium having a refractive index of n by a distance L.

The aluminum oxide film has a thickness that provides a desired reflectance at a desired oscillation wavelength , and the aluminum oxide film is provided for the wavelength of light when the thickness of the aluminum oxide film is constant. It is preferable that the thickness is set such that the slope is negative at the desired oscillation wavelength in the reflectance change curve of the end face.

  The thickness of the first dielectric film is set to a thickness that is not less than 0.6λ and not more than 1.5λ in terms of optical distance, and heat dissipation at the end of the stripe-shaped light emitting region is good, and This is also preferable because the change in reflectance can be suppressed even with respect to variations in film thickness during manufacturing.

  According to the present invention, since the dielectric film on the emission end face side is formed with a thickness that achieves a desired reflectivity and with an optical distance of 0.6λ or more, the stripe-shaped light emitting area end face is formed. The heat generated in the step can be effectively dissipated through the dielectric film, and the problem that the end face is excessively heated and damaged can be solved. That is, in the conventional semiconductor laser, the single-layer or multi-layer dielectric film is only provided on the emission side end face of the stripe-like light emitting region so as to obtain a desired reflectance so that a desired output is emitted. However, according to the present invention, not only to adjust the reflectance, but also to improve the heat dissipation at the end face, it is formed of only one layer of aluminum oxide having a thermal conductivity better than that of the semiconductor layer, and its thickness Can be dissipated from a large area by increasing the optical distance to 0.6λ or more. As a result, the temperature rise at the end face of the stripe-shaped light emitting region can be suppressed, the COD level can be improved, and even if aging is performed at a high temperature (75 ° C.) and a high output (200 mW), it takes 500 hours or longer. The semiconductor laser can continue to operate without being damaged for a long time, resulting in a very long-life semiconductor laser.

  Furthermore, in the present invention, the thickness of the first dielectric film is not only increased and the thickness is set so as to obtain a desired reflectance, but the thickness of the dielectric film when the wavelength is constant is set. The thickness is set so that the change in reflectivity with respect to the thickness is positive, or the change rate in reflectivity with respect to the wavelength when the thickness of the dielectric film is constant is set to a thickness that is negative. When the laser starts to operate, it has a characteristic that its oscillation wavelength becomes longer. However, for a slightly longer wavelength, the dielectric film having the same thickness has a lower reflectance. As a result, the output of the laser light emitted to the outside increases, and it is possible to cancel the decrease in output due to the increase in threshold current as the temperature rises, thereby improving the external differential quantum efficiency. Therefore, even if the temperature rises due to the operation of the laser chip, the laser chip can be operated with almost no decrease in the output emitted to the outside.

  Further, the reflectance on the first dielectric film side (front end face) described above is set to a low reflectance of about several percent, particularly in a high-power semiconductor laser, and therefore only to be set to a desired reflectance. When the oscillation wavelength is shifted to the longer wavelength side by setting the reflectance to the thickness of the dielectric film to be positive, the reflection with respect to the thickness of the dielectric film will be described later. The rate is shifted to the minimum side, and the change in reflectance can be suppressed to a small level. That is, the reflectance is small and the reflectance is close to the minimum of the reflectance curve, and the change in reflectance is large on the side opposite to the minimum side, but the change in reflectance is small on the minimum side. Even when shifted to, the deviation in reflectance can be kept small.

  Next, the semiconductor laser of the present invention will be described with reference to the drawings. A semiconductor laser according to the present invention is laminated on a semiconductor substrate 1 so as to form a stripe-shaped light emitting region and oscillate at an oscillation wavelength λ as shown in FIG. Semiconductor layers are stacked to form a semiconductor stacked portion 9. Then, the first dielectric film 17 is formed at one end of the stripe-like light emitting region (see the beam spot P in FIG. 1B) of the semiconductor laminated portion 9 so that the reflectance is lowered to a predetermined reflectance. A second dielectric film 18 is formed on the other end portion of the stripe-shaped light emitting region so as to increase the reflectivity and increase the reflectivity. In the present invention, the first dielectric film 17 is formed of an aluminum oxide film, and the thickness of the aluminum oxide film is a curve of reflectivity change with respect to the thickness of the aluminum oxide film with a constant oscillation wavelength λ. The thickness is such that the slope of the reflectance change curve is positive, and the optical distance is 0.6λ or more, preferably 0.7λ or more, more preferably 0.8λ or more. It is characterized by being set to.

  As described above, the present inventors have found that when a semiconductor laser starts operating, the oscillation wavelength becomes longer, and the output decreases due to a change in reflectance due to the shift of the oscillation wavelength. In order to solve the problem of the semiconductor laser being easily destroyed in a short time when the accelerated life test was conducted, intensive studies were repeated. As a result, with the conventional thickness of the dielectric film provided on the end face, the reflectance increases further as the oscillation wavelength becomes longer, and the output is further reduced due to the larger change rate, By adopting the thickness of the dielectric film that makes the reflectance change negative with respect to the wavelength change in the vicinity of the desired wavelength, the change in reflectance is small when the oscillation wavelength changes in the longer direction. In addition, since the reflectance itself also changes in the direction of decreasing, the external differential quantum efficiency can be improved, the output decrease due to the change of the oscillation wavelength can be suppressed, and the heat dissipation generated at the cleaved end face of the laser chip is not sufficient. The semiconductor crystal on the cleavage plane is melted by the heat and the end face is destroyed. However, heat dissipation is achieved by increasing the thickness of the first dielectric film 17 using aluminum oxide having good thermal conductivity. That can suppress damage due to COD and can sufficiently perform, found.

That is, when the first dielectric film 17 has a single layer structure of aluminum oxide (Al ₂ O ₃ ) and the thickness provided on the cleavage plane of the stripe-shaped light emitting region is variously changed, the wavelength of light is 780 nm. As shown in FIG. 2, when the thickness t of the first dielectric film 17 is changed, the reflectance changes periodically as shown in FIG. To do. Conventionally, since the first dielectric film 17 is formed by sputtering or the like, it takes about 3 minutes to deposit 10 nm, and it takes time. Therefore, a desired reflectance (for example, 8.5% at 780 nm) is obtained. The initial thickness of about 90 nm was employed.

  However, at a long wavelength of 790 nm, as shown by B, the curve is almost parallel to the right, and as can be seen, in order to obtain the same reflectance, the thickness of the dielectric film is increased. There is a need. On the other hand, when the first dielectric film 17 having the thickness adjusted to the desired reflectance at 780 nm is provided and the oscillation wavelength changes and becomes longer, the thickness of the dielectric film does not change. The reflectance becomes higher than the initially set reflectance (the position is b1 in FIG. 2). As a result, the external differential quantum efficiency decreases and the output output decreases.

  Therefore, the present inventor not only sets the thickness of the dielectric film to have a predetermined reflectance, but also has a relationship in which the change in reflectance becomes small when the oscillation wavelength changes long. This problem was solved by adopting the thickness of. That is, as shown in FIG. 2 described above, the reflectivity of the front end face is set to a low reflectivity so that the front end face can be emitted from the front end face as much as possible, particularly in a high-power semiconductor laser. Therefore, the reflectance is often set near the minimum point in the curve of the change in reflectance with respect to the thickness of the dielectric film, and the change in reflectance on the minimum point side with respect to the change in the thickness of the dielectric film However, on the side opposite to the minimum point, the change in reflectance with respect to the change in the thickness of the dielectric film increases.

  On the other hand, the reflectance curve for the same film thickness when the wavelength is long is slightly shifted toward the thicker film thickness as shown by B in FIG. Therefore, for example, even when the wavelength is 780 nm, even when the reflectance is the same (a1, a2, a3, a4 in FIG. 2), the slope of the reflectance curve is positive (dRf / dt> 0) (a2, a4 in FIG. 2). If so, the reflectance approaches a minimum direction for light having a long wavelength at the thickness (b2 and b4 in FIG. 2), and the change in reflectance becomes small. For this reason, when the oscillation wavelength becomes longer due to the operating temperature, the reflectance Rf itself becomes smaller at that wavelength, the external differential quantum efficiency increases, and the threshold current increases due to the temperature rise to compensate for the oscillation output that decreases. .

  In the above examination, a method corresponding to a change in the oscillation wavelength of the semiconductor laser was examined by setting the reflectance in a direction in which the reflectance hardly changes due to a change in the reflectance Rf with respect to the film thickness t of the dielectric film. As described above, when the temperature rises due to the operation of the semiconductor laser, the threshold current increases and the output decreases. For this reason, when the oscillation wavelength becomes longer due to the temperature rise, the output change due to the temperature rise can be corrected by setting the film thickness so that the reflectance Rf due to the dielectric film is lowered. That is, for example, when the wavelength of light is changed with the film thickness at a predetermined reflectance Rf being constant, the reflectance Rf is periodically changed by the change of the wavelength λ as shown in FIG. Therefore, for example, by adopting the thickness t at which the change rate (dRf / dλ) of the reflectance Rf with respect to the wavelength at a desired wavelength, for example, around 780 nm is negative among the thicknesses at which the desired reflectance is obtained, The output change due to the rise can be offset.

  Note that if the absolute value of the change rate (dRf / dλ) of the reflectance Rf with respect to the wavelength λ is too large, even if the gradient is negative, the change in reflectivity becomes too large, so −1 ≦ (dRf / dλ ) <0. By selecting the film thickness of the dielectric film so as to achieve a desired reflectivity from FIG. 2 while satisfying such conditions, the oscillation efficiency decreases with the increase in temperature due to the operation of the semiconductor laser. An output change can be suppressed.

  Further, as described above, the heat dissipation can be improved by making the thickness of the dielectric film above a certain level, and the COD level can be kept very high even in a high-power semiconductor laser. Even when aging at 75 ° C. and high output (200 mW) was performed for 500 hours or more, it was not destroyed. That is, as a first dielectric film, aluminum oxide having a high thermal conductivity is used, and its thickness is variously changed. The result of examining how the COD characteristics change is shown in FIG. And a thickness of 0.6λ or more (when the refractive index n of aluminum oxide is 1.62 for a wavelength of 780 nm, the thickness t of the physical dielectric film is 289 nm or more), preferably optical When the distance is set to 0.7λ or more, more preferably, the optical distance is set to 0.8λ or more, sufficient heat dissipation can be achieved, and the above-described accelerated aging is performed using a high-power semiconductor laser of 250 mW or more. However, 30 were damaged in 500 hours, and none were generated.

  From the viewpoint of heat dissipation, the thicker the dielectric film, the better. However, if it is too thick, it takes time to form the film and the cost is increased, and it is difficult to accurately control the reflectance with the thick dielectric film. Therefore, the optical distance is preferably 1.5λ or less. Specifically, when the reflectance is set to 8.5%, the optical distance is set to 0.83λ (the physical thickness of the aluminum oxide film is 0.83λ / n = 400 nm), so that the output due to the temperature rise. The impact on change was reduced, and the service life could be very long.

The second dielectric film 18 provided on the rear end face reflects most of it and oscillates in the resonator so that a large output can be taken out from the front end face side. as it becomes about to 95% alpha-Si (refractive index of lambda is the oscillation wavelength, n represents the dielectric film) (amorphous silicon) film and, Al ₂ O ₃ film and the respective lambda / (4n) of the increments thickness About 2 sets are formed. However, the rear end face only needs to obtain a desired reflectance Rr, and is not limited to the material or combination of the dielectric films.

  The semiconductor substrate 1, the semiconductor laminate 9 and the electrodes 15 and 16 have the same structure as a conventional general semiconductor laser. As the semiconductor laminate 9, for example, an AlGaAs compound for infrared light having a wavelength of 780 nm is used. A semiconductor or an InGaAlP compound semiconductor that emits red light at 650 nm wavelength is used, and a GaAs substrate is generally used as the semiconductor substrate 1 for stacking these semiconductor materials. I do not care. In addition, the conductivity type of the semiconductor substrate 1 is either n-type or p-type of the desired conductivity type on the substrate side in relation to the set incorporating the semiconductor laser. The conductivity type of the semiconductor layer to be formed is also determined. In the following specific example, the semiconductor substrate 1 will be described as an n-type example.

  In the example shown in FIG. 1, the semiconductor laminated portion 9 includes an n-type cladding layer 2, an undoped or n-type or p-type active layer 3, a p-type first cladding layer 4, a p-type etching stop layer 5, p. Of the n-type current blocking layer 13, the cap layer 7 and the current blocking layer 13 embedded on both sides of the p-type second cladding layer 6 etched into a ridge shape. The p-type contact layer 8 is provided on the surface.

Specifically, the n-type GaAs substrate 1 is placed in, for example, a MOCVD (metal organic chemical vapor deposition) apparatus, and reactive gases such as triethylgallium (TEG), trimethylaluminum (TMA), trimethylindium (TMIn), phosphine ( Depending on the conductivity type of PH ₃ ), arsine (AsH ₃ ) and the semiconductor layer, the required material of H ₂ Se as an n-type dopant gas or dimethyl zinc (DMZn) as a p-type dopant is changed to hydrogen (H ₂ ) And epitaxially growing each semiconductor layer at about 500 to 700 ° C. to obtain the above-described stacked structure of each semiconductor layer.

The n-type cladding layer 2 is made of, for example, Al _x1 Ga _1-x1 As (0.3 ≦ x1 ≦ 0.7, for example, x1 = 0.5), and is formed to have a thickness of about 2 to 4 μm. _{y1 Ga 1-y1 As (0.05} ≦ y1 ≦ 0.2, for example y1 = 0.15) bulk structure or _{Al y2 Ga 1-y2 As (} 0.01 ≦ y2 ≦ 0.1 , such y2 = 0 0.05) and a barrier layer made of Al _y3 Ga _1-y3 As (0.2 ≦ y3 ≦ 0.5, y2 <y3, for example y3 = 0.3) The p-type first cladding layer 4 is formed of Al _x2 Ga _1-x2 As (0.3 ≦ x2 ≦ 0.7, for example, x2) by the SQW or MQW structure. = 0.5) is formed to be about 0.1 to 0.5 μm. Other semiconductor layers such as a structure in which a light guide layer is provided between the active layer 3 and the cladding layers 2 and 4 may be interposed between any of the layers.

Further, an etching stop layer 5 is formed on the p-type first cladding layer 4 to a thickness of about 0.01 to 0.05 μm by p-type or undoped, for example, In _0.49 Ga _0.51 P, and the p-type second cladding layer 6 is formed. , Al _x3 Ga _1-x3 As (0.3 ≦ x3 ≦ 0.7, for example, x3 = 0.5), and a cap made of p-type In _0.49 Ga _0.51 P on the order of 0.5 to 3 μm. The layer 7 is provided in a thickness of about 0.01 to 0.05 μm, and both sides of the cap layer 7 and the p-type second cladding layer 6 are etched to form the ridge portion 11, and on both sides, for example, Al _z Ga _1-z As A current blocking layer 13 made of (0.5 ≦ z ≦ 0.8, for example, z = 0.6) is formed so as to fill the side of the ridge portion 11.

The etching stop layer 5 is not limited to In _0.49 Ga _0.51 P. For example, In _0.49 (Ga _0.8 Al _0.2 ) _0.51 P can be used, and the cap layer 7 is formed in a later step. When the contact layer is grown, an oxide film or the like is formed on the surface of the semiconductor stacked portion 10 to prevent contamination, and other semiconductor layers such as GaAs may be used, and even the surface contamination is prevented. If you can, you do not have to. Etching for forming the ridge portion 11 is performed by, for example, forming a mask made of SiO ₂ or SiN _x by, for example, a CVD method, selectively etching the cap layer 7 by, for example, dry etching, and the like. By etching the p-type second cladding layer 6 with such an etchant, the ridge portion 11 is formed in a stripe shape (in the direction perpendicular to the paper surface) as shown in the figure. In addition, the exposed etching stop layer 5 may be removed.

  The contact layer 9 is formed on the cap layer 7 and the current blocking layer 13 by a p-type GaAs layer, for example, with a thickness of about 0.05 to 10 μm. A p-side electrode 15 made of Ti / Au or the like is formed on the surface of the contact layer 9, and the back surface of the semiconductor substrate 1 is made of Au / Ge / Ni or Ti / Au after being thinned by polishing. N-side electrodes 16 are formed. After this electrode formation, the wafer is chipped by cleavage or the like.

In the above example, an AlGaAs-based compound semiconductor is used. However, in the case of an InGaAlP-based compound, In _0.49 (Ga _{1 -u} Al _u ) _0.51 P ( 0.45 ≦ u ≦ 0.8 (for example, u = 0.7) is used as the active layer, and In _0.49 (Ga _{1 -v1} Al _v1 ) _0.51 P (0 ≦ v1 ≦ 0.25, for example, v1 = 0) / In _0.49 (Ga _{1 -v 2} Al _{v 2} ) _0.51 P (0.3 ≦ v2 ≦ 0.7, for example, v2 = 0.4), etc. In addition, as a current blocking layer, GaAs or Except for forming by using InAlP, it can be configured in the same manner as the above-described example.

  In the above-described example, the semiconductor laser has a ridge structure. However, a semiconductor having another structure such as a SAS structure in which a current blocking layer is stacked between clad layers and a stripe groove serving as a current injection region is removed by etching. It goes without saying that the same applies to lasers.

  According to the present invention, as described above, the dielectric film provided on the front end portion (outgoing side) end face of the stripe-shaped light emitting region is not provided only for the purpose of setting the predetermined reflectivity, but sufficiently dissipates heat. In order to be able to increase the COD level, the dielectric layer is formed on the output end face side so that the output change is suppressed even when the oscillation wavelength shifts due to the operation. A body membrane is provided. As a result, a semiconductor laser having a very long lifetime and stable output characteristics can be obtained.

  The present invention can be used for a light source for pickup such as a CD, DVD, DVD-ROM, and data-writable CD-R / RW, and can be used for electrical equipment such as a personal computer.

It is explanatory drawing of the perspective view and cross section which show one Embodiment of the semiconductor laser of this invention. It is a figure which shows the change of the end surface reflectance with respect to the thickness of a dielectric film when a wavelength is made constant. It is a figure which shows the change of the end surface reflectance with respect to a wavelength when the thickness of a dielectric material film is made constant. It is a figure which shows the change of the COD characteristic with respect to the thickness of a dielectric film. It is the figure which mounted the conventional semiconductor laser in the submount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 9 Semiconductor laminated part 17 1st dielectric film 18 2nd dielectric film

Claims (3)

A semiconductor substrate, a semiconductor laminated portion laminated on the semiconductor substrate to form a stripe-like light emitting region, and a semiconductor layer laminated so as to oscillate at an oscillation wavelength λ, and the stripe-like light emission of the semiconductor laminated portion A first dielectric film formed at one end of the region to have a predetermined reflectance with a low reflectance, and a first dielectric film formed to have a high reflectance at the other end of the stripe-shaped light emitting region. and a second dielectric layer, said first dielectric film is formed by an aluminum oxide film, before SL curve reflectance change relative to the thickness of the aluminum oxide film the oscillation wavelength λ as constant, the oscillation wavelength In the case where the aluminum oxide film moves almost parallel to the thicker one when the length is increased, the reflectance change curve has a desired reflectance for the desired oscillation wavelength , and the reflection Of the rate change curve The thickness gradient is positive, the by Rukoto set the thickness of the aluminum oxide film, the output due to an increase in threshold current due to the temperature rise by lowering the reflectance due to the change in the oscillation wavelength due to temperature rise A semiconductor laser that corrects the decrease and is set to a thickness that is 0.6λ or more in optical distance. The aluminum oxide film has a thickness that provides a desired reflectance at a desired oscillation wavelength , and the aluminum oxide film is provided for the wavelength of light when the thickness of the aluminum oxide film is constant. 2. The semiconductor laser according to claim 1 , wherein the thickness is set to a thickness at which the slope is negative at the desired oscillation wavelength in the curve of the reflectance change of the end face.   3. The semiconductor laser according to claim 1, wherein the thickness of the first dielectric film is set to an optical distance of 0.6λ or more and 1.5λ or less.

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